FEATURES

FAMILY

DESCRIPTION

Also known as HEXB_HUMAN, HEXB. Hydrolyzes the non-reducing end N-acetyl-D-hexosamine and/or sulfated N-acetyl-D-hexosamine of glycoconjugates, such as the oligosaccharide moieties from proteins and neutral glycolipids, or from certain mucopolysaccharides (PubMed:11707436, PubMed:9694901, PubMed:8672428, PubMed:8123671). The isozyme B does not hydrolyze each of these substrates, however hydrolyzes efficiently neutral oligosaccharide (PubMed:11707436). Only the isozyme A is responsible for the degradation of GM2 gangliosides in the presence of GM2A (PubMed:9694901, PubMed:8672428, PubMed:8123671). During fertilization is responsible, at least in part, for the zona block to polyspermy. Present in the cortical granules of non-activated oocytes, is exocytosed during the cortical reaction in response to oocyte activation and inactivates the sperm galactosyltransferase-binding site, accounting for the block in sperm binding to the zona pellucida (By similarity). There are 3 forms of beta-hexosaminidase: hexosaminidase A is an heterodimer composed of one subunit alpha and one subunit beta (chain A and B); hexosaminidase B is an homodimer of two beta subunits (two chains A and B); hexosaminidase S is a homodimer of two alpha subunits (By similarity). The composition of the dimer (isozyme A versus isozyme S) has a significant effect on the substrate specificity of the alpha subunit active site (PubMed:8672428).

EXTERNAL LINKS

HEXB

Beta-hexosaminidase subunit beta

HEXB

Molecular Synopsis